Research on involvement of public transit customers, which can be defined as the level of interest or importance of public transit to a passenger, is scarce and no study has attempted to comprehensively analyze this concept in the public transit sector. Based on behavioral and marketing literature, this paper tests three possible roles of involvement in regards to passengers' perceptions of a Light-Rail Transit (LRT) service in Seville (Spain): the mediator, moderator and antecedent roles. The structural equation modeling approach was used to test the conditions of mediation and moderation in social psychology and to evaluate the theoretical relationships of involvement as an antecedent. A nested model strategy allowed us to compare competing models and a multiple group analysis was conducted to test for moderation. Our results indicate that involvement of public transit users could positively affect their evaluations of the service quality, and enhance their intentions to reuse the service and recommend it to others. Furthermore, involvement could also moderate the direct effect of service quality perceptions of highly involved users on their behavioral intentions. Consequently, higher levels of involvement could lead perceptions of service quality to affect positive behavioral intentions mainly through customer's satisfaction. Furthermore, the level of product hierarchy at which passengers make their decisions to use a transportation mode may affect how they make their evaluations and decisions in regards to that mode. These results lead to important and practical considerations for transportation managers who aim to enhance passengers' intentions to reuse the service and recommend it to others. The insight gained with this paper in regards to the effect of involvement on passengers' perceptions may allow the design of effective marketing strategies that aim to grow transit ridership by increasing the importance of public transit for passengers.